The work to be accomplished encompasses: (1) A series of studies to characterize heterogeneities in cardiac microvascular form and regional blood flows, using morphonetric techniques combined with microsphere-based measures of local flow, using new fractal autocorrelation techniques to determine the directionality of the correlations among local flows, and determining flow heterogeneity at high spatial resolution in large hearts. (2) To develop the methods of analysis for interpreting signals from 150- oxygen, 150-water, and 150-carbon monoxide residue functions (by PET imaging) in the heart and t he methods for estimating regional oxygen consumption from these hearts and displaying parametric images of such features as local oxygen metabolic rate, vascular volumes, and permeability-surface area products. (3) A series of studies to determine if increased myocardial metabolism reduces the degree of flow heterogeneity in the heart overall in sheep during control states, adrenergic stimulation and atrial pacing. This research, in collaboration with PET imaging studies requires service support in radioisotope chemistry, in physics of PET imaging (equipment maintenance and software development) and in imaging procedures, all of which are in collaboration with personnel in Nuclear Medicine and Radiology. The results should provide not only new insight into the nature of flow heterogeneity in the normal heart but also improved resolution in interpreting images of cardiac metabolic processes.